The agent that is responsible for the sensation of heat felt after eating hot sauce is capsaicin. Capsaicin binding to what are known collectively as TRP-family receptors transduce the capsaicin stimulus into an intracellular message that leads to the sensation of heat! The effect does not stop there, although more prolific when delivered as a nasal spray, capsaicin interacting with it's appropriate receptor also leads to sinus relief.1
So microwaves work by spitting out (emitting) high frequency electromagnetic waves. Electromagnetic waves have the effect, in this context, of transferring energy into the food. Water is a polar molecule, meaning to say that it has partially positive and negative ends to it, similar to a magnet, which has a north end to it and a south end to it. When the waves encounter the food, the water reorients itself to be aligned with the same polarity of the electromagnetic waves being spit out by the microwave. In the process of this reorientation, it transfers energy via friction, thereby heating your food. Some of this water is lost as evaporation, and thus placing a wet paper towel on top of the food will serve as a source of water, which said food will absorb as water is lost.2 If that was hard to visualize, it the same kind of process that occurs when you use a compass, the compass moves to point toward the north and south poles as you turn, except in the compass there is very little resistance to it's reorientation, hence it doesn't generate heat upon spinning.
Most people don't give a thought to the type of toothpaste they use, probably because someone has been buying it for them their entire life. The most common toothpaste in the U.S. is Colgate Total + Whitening.3 The component which confers the whitening effects to this toothpaste (and many others) is hydrogen peroxide. The hydrogen peroxide, while an effective bleaching agent, can degrade the enamel coating your teeth, thereby leading to sensitivity. For kicks, I'd like to inform you that hydrogen peroxide is also used your cells to degrade waste products. The solution? Sensodyne toothpaste is one that worked for me.
Bookstand. Bookstands are love. Bookstands are life. I was going to go into the science behind this, but I will back off and let you think about it.
1. Blom, HM, and LA Severijnen. "The Long-term Effects of Capsaicin Aqueous Spray on the Nasal Mucosa. - PubMed - NCBI." National Center for Biotechnology Information. Accessed January 20, 2016. http://www.ncbi.nlm.nih.gov/pubmed/9824407.
2. Fitzgerald, Tom. "Probing Question: How Do Microwaves Cook Food? | Penn State University." News | Penn State University. Accessed January 20, 2016. http://news.psu.edu/story/141277/2005/11/28/research/probing-question-how-do-microwaves-cook-food.
3. "Leading Toothpaste Brands in the U.S. 2014 | Statistic." Statista. Accessed January 20, 2016. http://www.statista.com/statistics/195650/leading-us-toothpaste-brands-in-2007-and-2008-based-on-sales/.